The invention relates to methods and articles for determining print quality of an invisible ink encodement recorded by a printer on media, particularly a test print recorded in invisible ink or dye by a printer, to enable a user to determine if the ink or dye is depleted or the printer is operating improperly.
It is well known to imprint data on various articles and objects, including printed media, labels, containers, vehicles, etc., in the form of a machine readable, code or xe2x80x9csymbologyxe2x80x9d that is visible to the eye but requires a reader to read and decode. The terms xe2x80x9csymbologyxe2x80x9d or xe2x80x9csymbologiesxe2x80x9d are generally employed to denote spatial patterns of symbology elements or marks, wherein each mark has a shape and separated from an adjacent mark by a spacing between the marks, whereby information is encoded in the shapes and/or the spacings between the marks, and embrace bar codes and other codes as described further below. Typically the decoded information output by the reader is used by a machine in a process of identification of the article and to associate it with other data, e.g. unit price and restocking code, which may be displayed and printed out. A great many symbologies and specialized symbology readers have been adopted over the years.
It is also known to encode aural information as such machine readable bar codes associated with images on media so that the aural information or sound can be reproduced from the encoded symbology. Such systems are shown, for example, in U.S. Pat. Nos. 5,276,472 and 5,313,235 in relation to photographic prints, and in U.S. Pat. Nos. 5,059,126 and 5,314,336 in relation to other objects or printed images.
Furthermore, it is well known to record or print symbologies or human recognizable images on various media, e.g., documents, identity cards, financial instruments, professional photographic prints, etc., to verify identity or inhibit unauthorized use or copying, and on stamps and envelopes in postal cancellation applications. Such printing is typically done with one or more invisible ink or dye imprinted on the surface of the document or incorporated into internal layers of the media. These symbologies or recognizable images are normally invisible but can be made visible to and read by a scanner or reader when illuminated by a specific light wavelength or band, e.g. infrared and ultraviolet wavelengths. Such symbologies or images are intended to be permanently recorded or printed onto or incorporated within the media and to be tamper resistant.
The above-referenced, commonly assigned and pending patent applications disclose encoding xe2x80x9cvariable dataxe2x80x9d in conformance with a known symbology and printing it as an invisible xe2x80x9cencodementxe2x80x9d located in an image field on media on a photographic print image or a print that is produced by other means. One disclosed use of such invisible encodements constitutes printing the invisible encodements over or with a visual print image at the time that prints are made from filmstrip image frames. Typically, such prints would be made for consumers (hereafter referred to as users) from such filmstrips by photofinishers. In this context, the term xe2x80x9cvariable dataxe2x80x9d includes data that varies from print to print and contains information typically related to the visible print image. The xe2x80x9cencodementxe2x80x9d is preferably encoded and printed using a two-dimensional symbology that is relatively dense and is at least co-extensive in area with the visible photographic image to maximize the amount of sound information that can be recorded.
The encodement is invisible or substantially invisible to the human eye when viewed under normal viewing conditions, that is, facing the viewer and under sunlight or normal room illumination such as incandescent lighting. This ensures that the encodement does not materially degrade the visible print image. A number of encodement materials and encodement printing techniques are disclosed in the above-referenced commonly assigned and pending patent applications. It is contemplated that the preferred encodement materials would be infrared absorbing inks or dyes imprinted onto the visible print image using thermal dye transfer printing or inkjet or laser printing techniques or the like.
But, it is also contemplated that the user may alternatively generate variable data and print such invisible encodements over a visible print image using computer based printer systems of the types disclosed in the above-incorporated U.S. patent application Ser. Nos. 08/931,575, and 09/356,956. In this context, users may also generate the variable data and visible image data from a variety of sources and print them on print media.
For example, digital cameras are available for use by such users that capture digital image data when used and also have the capability of recording user input sound information and camera input exposure information at the time the image is captured by the user. Software implemented typically in a personal computer is employed to process the digital image data and display the images on a monitor for editing and to make permanent prints of such digitally captured images employing inkjet or laser color printers or thermal dye transfer printers.
The user that receives such a print with the invisible encodement made by a photofinisher or that prints an encodement onto visible print image would employ a playback unit to capture the encodement and reproduce or play back the sound or display the visual information or otherwise use the variable data of the encodement. The above-incorporated U.S. patent application Ser. Nos. 08/931,575, and 09/356,956 also disclose systems for reading encodements of this type. During reading, the invisible encodement image is illuminated with light having a wavelength that causes the invisible dye to absorb or reflect the light or to fluoresce in contrast to the background of the media. The illuminated encodement image is captured by a planar imager, e.g. a CCD or CMOS array imager of a hand held reader or a stationary reader or scanner. The variable data of the captured encodement image is decoded and played back as sound through various sound reproduction systems or displayed in visible form to be read by the user.
The user that records an invisible encodement using such a user operated printer has no way of knowing whether the ink or dye is being printed on the print media because it is invisible to the eye. The invisible encodement may be entirely missing or so badly or faintly printed that it cannot be accurately read. The invisible ink or laser toner or thermal dye transfer media may become exhausted or the cartridge or printing head may otherwise become defective and smear or erratically print symbology elements of the encodemnent. After the invisible encodement is printed, it is possible to employ the scanner or reader to determine if the encodement can be read. But, even if the encodement can be read, there is no simple or inexpensive way to determine if the print quality of the encodement is high enough to avoid deterioration over time due to ink or dye fading or to allow a certain amount of handling of the print, for example, and still allow successful reading of the encodement. If the encodement print quality is so poor that errors are detected when it is read, it is difficult to remove the encodement or to reprint the encodement using a new ink cartridge or dye transfer media over the existing encodement due to possible misalignment of the print media during such reprinting.
There is a need for inexpensive and simple methods and articles that enable the user to determine the invisible ink print quality that the printer is capable of providing before or following printing of a desired invisible encodement on the print media.
The invention is defined by the claims. The invention, in its broader aspects, provides: (1) a test target having a plurality of invisible encodements each comprising test data printed over a test print media in a defined spatial order by the printer under test, wherein the print quality of the printer is determined by the ability of the reader to decode the plurality of invisible encodements; and (2) methods of generating and reading the test target.
The invention may be practiced employing any printer technology capable of printing invisible encodements including but not limited to thermal dye transfer printers, inkjet printers, laser printers and the like. For purposes of simplifying the description and claims, the term xe2x80x9cinkxe2x80x9d will be employed herein to embrace inks, dyes, toners and the like that can be employed in printing invisible encodements as described above.
In a first preferred embodiment, a test print media is prepared by pre-printing or coating a media surface with an invisible ink that is sensitive to the same wavelength of light as the printer ink in a plurality of densities in a plurality N of spaced apart areas of the media surface providing step background densities in a test tablet manner. The background densities range from no applied ink to maximum printer ink density in N increments. In the test mode, N test data files are printed as N invisible encodements in the corresponding N areas of the test print media all at the same maximum print density that the printer is capable of providing, thereby creating a test target that is to be read by the reader. Because of a difference in contrast, a predetermined number of the encodements at defined locations where the density of the encodement exceeds the step densities by a certain amount are readable if the print quality is less than maximum print quality. The particular ones of the encodements that can be accurately decoded provide a measure of the print quality that the printer is capable of achieving. It is presumed that the print quality that the printer is capable of achieving is degraded if fewer than the predetermined number of encodements are readable, and the invisible ink is replaced or replenished.
In a second preferred embodiment, the test target comprises a plurality of encodements differing from one another in a step tablet manner printed by the printer under test on test print media that can comprise plain paper or paper or prints bearing visible images that can be sacrificed. Each of the encodements is read and decoded to the extent possible using the reader. The particular ones of the encodements that can be accurately decoded provide a measure of the print quality that the printer is capable of achieving.
In one variation of this embodiment, a series of test data files are printed with varying degrees of symbology element intensity or density of applied invisible ink by a gray scale print mode program installed in the computer controlling the printer in question. In the test mode, the test data files are thereby printed as a plurality of progressively degraded or more faded invisible encodements at a corresponding plurality of discrete locations of the test print media thereby creating a test target that is to be read by the reader. At maximum print quality, a predetermined number of the encodements at defined locations are readable despite the imposed degradation of print quality. Additional physical corruption of the encodements occurs if print quality is reduced from maximum print quality. Again, it is presumed that the print quality that the printer is capable of achieving is degraded if fewer than the predetermined number of encodements are readable or a predetermined encodement is not readable.
In a further variation of this embodiment, a series of test data files are created with varying amounts of corrupted data by a test program installed in the computer controlling the printer in question. In the test mode, the test data files are printed as a plurality of invisible encodements at a corresponding plurality of discrete locations of the test print media thereby creating a test target that is to be read by the reader. Given that redundancy is built into the encoding, a predetermined number of the encodements at defined locations are readable despite the imposed corruption at maximum print quality. Additional physical corruption of the encodements occurs if print quality is degraded from maximum print quality. Again, if fewer than the predetermined number of encodements are readable, it is presumed that the print quality that the printer is capable of achieving is degraded.
In a still further variation of this embodiment, a series of test data files are printed as invisible ink encodements with varying degrees of symbology element resolution, including element size and spacing, by a resolution changing program installed in the computer controlling the printer in question. In the test mode, the test data files are thereby printed as a plurality of progressively higher resolution invisible encodements at a corresponding plurality of discrete locations of the test print media thereby creating a test target that is to be read by the reader. At maximum print quality, a predetermined number of the encodements at defined locations are readable despite the sequential increase in resolution. Physical corruption of the encodements occurs if print quality is reduced from maximum print quality. Again, it is presumed that the print quality that the printer is capable of achieving is degraded if fewer than the predetermined number of encodements are readable or a predetermined encodement is not readable.
In each embodiment, the user can use the reader to capture each encodement, and the user is advised if the reader can decode the encodement audibly and/or visually. The audible or visual message that is encoded in each encodement that can be read advises the user of print quality and preferably constitutes the statement of the quality of the printer which can also be printed visibly on the test target in physical association with the encodements.
The use of such test print media and the methods of printing and reading the same provide the user with simple and inexpensive ways to gauge the invisible ink print quality in advance of printing an invisible encodement. A new ink container or source or other corrections of the printer can be pursued if the test reveals that print quality is degraded. The invention provides a high degree of flexibility and choice in printing invisible encodements on a visible print or on other media.